192 Clinical Mledicline

Cheyletiella blakei, an Ectoparasite of Cats, as Cause of Cryptic Arthropod Infestations Affecting Humans BENJAMIN KEH, MS, and ROBERT S. LANE, PhD, Berkeley, and SHERRY P. SHACHTER, DVM, Alameda, California Cheyletiella blakei, an ectoparasitic mite of domestic cats, can cause an extremely annoying, persis- tent and pruritic dermatosis of obscure origin (cryptic infestation) in susceptible persons having close contact with infested cats. Although the prevalence ofcheyletiellosis in humans andcats appears to be low, evidence of its occurrence in California is increasing. Cheyletiellosis is often underdiagnosed in both its natural host and in humans. The small size of the mite, lack of publicity about the disease, frequentabsence ofsymptoms in infested cats andfailure to recover the mite from humans contribute to its delayedrecognition. When C blakei or other mites are suspectedofbeing the cause ofa dermatosis, medical entomologists may help to hasten the diagnosis by examining the patient's physical surround- ings, potential vertebrate hosts and other sources for the presence of mites. After C blakei has been eliminatedfrom cats with an appropriate pesticide, the disease in humans is self-limiting. (Keh B, Lane RS, Shachter SP: Cheyletiella blakei, an ectoparasite of cats, as cause of cryptic arthropod infestations affecting humans. West J Med 1987 Feb; 146:192-194)

Several mites including Cheyletiella blakei, * a widely dis- be aware of its existence. The frequent lack of obvious symp- tributed ectoparasite of domestic cats, are capable of toms in the natural host, the domestic cat, also contributes to causing cryptic infestations in humans. 1-3 This mite and the the failure of patients to recognize the specific cause of their related Cheyletiella yasguri on dogs produce a skin condition dermatitis. In our experience and that of others, dermatoses referred to as cheyletiellosis. We refer to such infestations on caused by Cheyletiella mites are commonly underdiagnosed humans caused by either species as human cheyletiellosis, on in patients.410 cats caused by C blakei as feline cheyletiellosis and on dogs The first published account of the occurrence of C blakei caused by Cyasguri as canine cheyletiellosis. in California appeared in 1975.6 In that infestation, a mother Typically, members of a household in which one or more and her 5-year-old daughter were afflicted with the disease in infested cats live report persistent pruritic lesions (see below) Berkeley, Alameda County, in July 1974. Since then three but are unaware oftheir cause until Cblakei is found weeks or additional infestations involving one to five persons have months later. After this mite is eliminated from a cat, mem- come to our attention. These include cases in Palo Cedro, bers ofthe household recover quickly without treatment-that Shasta County (April 1979), Petaluma, Sonoma County (Au- is, the disease is self-limiting.4-8 gust 1979), and Berkeley (March 1985). The Shasta and Recovery of Cblakei from cats (or Cyasguri from dogs) is Sonoma County records are from the files of the California essential for establishing a diagnosis ofhuman cheyletiellosis. State Department ofHealth Services and were made available To our knowledge there has been no published account in to us through the courtesy ofMr Gail Grodhaus. which a diagnosis of this disease was made on the basis of The purpose of this communication is to alert the medical clinical evidence alone. Moreover, when a patient is unable to community to increasing evidence of C blakei occurrence in provide a clue as to the probable cause of the pruritus, and California, to present detailed case history information about when veterinarians do not detect the mite on a cat, the com- the latest outbreak, to summarize some of the difficulties in- plaint goes undiagnosed. herent in diagnosing human and feline cheyletielloses and to Among factors that tend to obscure the cause of feline call attention to methods used by medical entomologists in cheyletiellosis is the small size ofthe mite, which ranges to as investigating cryptic arthropod infestations. much as 500 microns in body length. Thus, the mites are Report of an Outbreak scarcely visible to the naked eye and are easily overlooked.8 9 Further, very few lay persons or medical practitioners seem to The patient, aged 44 years, her husband and a daughter live in Berkeley, California. They purchased a 4-month-old *Cheyletiella parasitivorax was originally the name applied to Cheyletiella mites white female Persian cat from a dealer in San Francisco in found on rabbits, cats and dogs. Smiley (Proc Entomol Soc Wash 1965; 67:75-79) mid-December 1984. About four weeks later the mother recognized Cheyletiella on cats as a distinct species and later likewise (Ann Entomol Soc Am 1970; 63:1056-1078) recognized Cheyletiella on dogs as distinct. Cparasi- began having pruritus that occurred daily during the late after- livorax remains one of two Cheyletiella species occurring on rabbits. noon. In early February she traveled out of the country and

From the Department of Entomological Sciences, University of California, Berkeley (Dr Lane), and the South Shore Pet Hospital, Alameda, California (Dr Shachter). Mr Keh has recently retired from the Vector Surveillance and Control Branch, California State Department ofHealth Services, Berkeley, Califomia. Reprint requests to Robert S. Lane, PhD, Department of Entomological Sciences, University ofCalifornia, Berkeley, CA 94720. e o o THE WESTERN JOURNALTHE WESTERNJOURNALOF MEDICINE * FEBRUARY 1987 14619872 * 146 * 2193~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~193 her symptoms ceased but resumed on her return three weeks Epidemiology and Diagnosis later. Existing data suggest that C blakei is probably cosmopol- Affected parts of her body included the breasts and ante- itan in distribution,11 is host-specific on cats"I and completes rior trunk down to the waist, the back and occasionally the its entire life cycle on cat fur and skin. 12 Its life away from its arms and legs. The lesions were urticarial papules that typi- host (on humans or in the environment) is transitory. The cally occurred in clusters of three or four. According to the possibility that free-living C blakei may occasionally cause patient, they were first observed soon after the onset of pru- dermatitis in susceptible persons cannot be discounted. Le- ritus and resembled mosquito bites. Rapid swelling and irrita- sions may develop in casual visitors to a home having an tion occurred in some affected areas, though other areas did infested cat without having direct contact with the cat either not react until the following day. She had difficulty breathing before the animal is treated or for a brief period afterward. 12 and experienced emotional distress. The lesions disappeared This possibility is suggested indirectly by a case involving C slowly over a period ofweeks. yasguri in which a child had hundreds of pruritic lesions after Her 7-year-old daughter was similarly, albeit less se- it had slept on a quilt used by an infested dog13 and, in another verely, affected. Her husband had a few lesions and reacted case, when the same mite was recovered from the floor, furni- only slightly. Similar lesions developed in two children who ture and a mattress. 4 were overnight guests, and the children reacted severely. There appears to be no authoritative explanation of how The mother consulted six physicians including three der- human skin lesions due to C blakei are produced. In some matologists, but was unsuccessful in obtaining a correct diag- instances, however, the distribution of skin lesions on the nosis. She had been treated with topical and systemic trunk and other body regions is noted to coincide with areas in administration of steroids and had transitory relief. The pa- contact with the infested cat. This observation suggests that tient strongly suspected that an unidentified arthropod was the the lesions are caused by bites ofthe mites. cause of her pruritus and reported that on one occasion the Not surprisingly, once an etiologic agent is recognized, pruritus had been more severe after her cat had shared her reports of its occurrence increase. Bjarke and co-workers8 bed. Additionally, on more than one occasion, pruritus and saw 37 cases ofhuman cheyletiellosis in a two-year period. In papular formation began within about 30 minutes after she California, canine and feline cheyletielloses are being seen had held her cat. Scabies had been ruled out but flea bites and with increasing frequency.'0 The true incidence ofthe disease hives were still being considered in the differential diagnosis in humans and pets in this state (and elsewhere in the western when a medical entomologist (R.S.L.) was contacted for as- United States) is not known, but it is probably not as un- sistance on March 21, 1985. common as suggested by the dearth of reports from this re- The asymptomatic cat had been treated with a bath of gion. 0.06% pyrethrins and 0.6% piperonyl butoxide (Theradex) Patients usually are of little help in providing information without apparent success. Two of us (R.S.L. and S.P.S.) on the probable source oftheir dermatitis. Bjarke and associ- subsequently examined the cat for Cheyletiella mites by first ates8 in referring to human cheyletiellosis said that among 37 treating it with a pyrethroid wash, 0.05% tetramethrin patients in 24 homes "only in two cases did the owners them- (Aqua-Methrin), and then brushing it with a toothbrush along selves suspect their dogs or cats as being the indirect cause of the spine and on both flanks anteriorly to the neck and posteri- their itching dermatitis." Thus, patients would very likely orly to the base of the tail. The brushing was examined in the seek the help ofa physician first rather than a veterinarian. laboratory (by R.S.L.) and 16 mites, identified as C blakei, If C blakei is not suspected as the cause of dermatosis in were found. The specific identification was confirmed by Pro- humans by either a physician or a veterinarian,3"- cheyletiel- fessor Deane P. Furman, University ofCalifornia, Berkeley. losis may go undiagnosed or be attributed to delusions of The cat was treated three times at weekly intervals with parasitosis or to other causes. In the present case, scabies 8 % methylcarbamate (Sendran), but the owner ofthe cat still could have also been easily ruled out because the patient reported some pruritus, though it was reduced appreciably. reported remission of her symptoms when she traveled Further treatment of the cat by M.R. Floyd, DVM, using abroad. Not infrequently, examination of lesions on the pa- 0.15% pyrethrins and 1.5% piperonyl butoxide (Para Pyre- tients or their distribution on the body have led to suspicions thrin Mist) finally ended the complaint. or assertions that the complaints were due to some unspecified Two other Persian cats at the pet shop, one of which had arthropod,' -'- were due to hives' or were not caused by been treated earlier with a lime-sulfur dip, were examined by Cheyletiella.'6 In other cases, the dermatitis was mistakenly one ofus (R.S.L.) for the presence ofmites. None was recov- attributed to, or was suspected ofbeing caused by, fleas on the ered from the brushings obtained from these cats. The treated pet.9'10'15 Scraping the skin of a patient to obtain mite speci- cat had been suspected ofhaboring mites because it had scabs mens is ineffective because the mites are not there for long, across its head and along its back. Moreover, lesions devel- the unusual record of C blakei recovery from skin notwith- oped on one ofthe wrists ofan employee ofthe shop who had standing."' Inexplicably, Cheyletiella species has also been previously brushed the cats. obtained from shakings from underclothes belonging to a Discussion woman who had no known contact with pets.'8 Human cheyletiellosis due to C blakei is a prime example In humans, pruritic lesions caused by C blakei are nor- of a cryptic arthropod infestation whose resolution is com- mally distributed on the anterior trunk, arms and legs-that is, monly arrived at circuitously even when mites are suspected often matching those parts of the body in contact with a cat as the cause. Methods used to ascertain the cause of this when held.3'5'8 In one case, the lesions occurred on the legs of acariasis have either failed or achieved success after varying a patient as a result ofa cat having slept at the foot ofthe bed.' periods of delay. Here we present what we believe to be a Helpful information that could be obtained while inter- more efficient, direct approach to the investigation of sus- viewing patients suspected of having cheyletiellosis is pected cheyletiellosis, preceded by a brief review of the epi- whether remission ofthe dermatitis occurs when the patient is demiology, diagnosis and treatment ofthe disease. away from home'7 and whether the complaint began after the 194 CHEYLETIELLA INFESTATION AFFECTING HUMANS cat was acquired3'9 and subsequently became more severe cellulose adhesive tape risks damage to them when they are after they handled it5'9 or shared a bed with it.4 Notably, not later removed to prepare them for scientific study. If they are all persons in an infested household or in close contact with an to be sent to a medical entomologist (or acarologist) for exam- infested cat are affected.S 17 ination, they should be preserved in 80% alcohol. Several While many infested cats are asymptomatic,1 others have mites should be sent to increase the likelihood of having both varying amounts of scale and may scratch themselves.4 5'1119 sexes available for diagnostic purposes and to detect the pos- The cats we saw exhibited no gross lesions, visible flakings on sible existence ofmultiple mite-species infestations. the skin or fur or dandruff. The percentage of cats found to be Information that should accompany specimens are the lo- infested with C blakei has varied in different studies, but cale, date of collection, vertebrate host and collector's name. reported infestation rates are typically low, such as 0.16% to A brief description of the complaint is also desirable. Accu- 16.7 % .20-22 mulation of these kinds of data will eventually result in better The presence of C blakei has been established by the re- understanding ofthe biology ofthis pestiferous mite. covery of this mite in dust samples taken from the dust bag of If a physician, by a combination of clinical evidence and a vacuum cleaner,6 brushings3 6'9'12'15'23 or combings5 from response to questions, is able to establish with reasonable fur, in cat feces24 or in skin scrapings from cats.9 These certainty that the dermatitis is due to Cblakei, then treatment procedures are more likely to be undertaken if it is suspected of the cat with an appropriate pesticide is indicated. On the that a cat is the source of the complaint or at least that an other hand, if an unknown arthropod is suspected as the cause arthropod is the probable etiologic agent. ofthe dermatitis, then we recommend that the case be referred to a medical entomologist for follow-up investigation. In Cal- Treatme,t ifornia and other western states, medical entomologists Cats have been successfully treated with a number of dif- knowledgeable about parasitic mites may be contacted ferent pesticides including DDT,4'51 7 derris,4 malathion,19'23 through some universities, university extension services or Mycodex with carbaryl,10 25 ronnel,6 lime-sulfur dip,10'25 health departments. methylcarbamate9 24 and pyrethrins. 19 Our experience in ob- REFERENCES serving the effects of pesticide treatments is too limited to 1. Lomholt S: To tilfaelde af dyrefnat hos mennesket (Cheiletiella parasiti- recommend any of them therapeutically except for 0.15% vorax). Hospitalstid 1918; 61: 1098-1099 (English trans in ref3) 2. 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CalifVet 1982; 36:9-12 pected potential 11. Bronswijk JEMH van, DeKreek EJ: Cheyletiella (Acari: Cheyletiellidae) of mites. When the arthropod causing the complaint is found and dog, cat and domesticated rabbit, a review. J Med Entomol 1976; 13:315-327 identified, the corrective measure is often straightforward. 12. Gething MA: Cheyletiella infestation ofthe cat. Vet Ann 1973, pp 152-155 Medical contribute if au- 13. Shelley ED, Shelley WB, Pula JF, et al: The diagnostic challenge of nonbur- entomologists ordinarily little, any, rowing mite bites. JAMA 1984; 251 :2690-2691 thoritative clinical information useful for differential diag- 14. Bronswijk JEMH van, Jansen LH, Ophof AJ: Invasion ofa house by the dog nosis. parasite Cheyletiella yasguri (Smiley 1965), a mite causing prurigo in man. Derma- When cats are tologica 1972; 145:338-343 suspected ofharboring Cblakei, we recom- 15. Lee BW: Cheyletiella dermatitis. Arch Dermatol 198 1; 117:677-678 mend that they be examined by placing them on a piece of 16. Kunkle GA, Miller WH, Jr: Cheyletiella infestation in humans. Arch Der- white paper, treating them with a pesticide containing quick- matol 1980; 116:1345 knockdown 17. Fernstrom AJB, Gentele H: Dermatitis caused by mites living on cats. Acta components, such as pyrethrins synergized with Paediatr 1960; 49:752-753 piperonyl butoxide, brushing them and inspecting the brush- 18. Hewitt M, 'Urk SM: Cheyletiella sp. in the personal environment. Br J ings in 80% ethanol with a binocular microscope. Mites on Dermatol 1974; 90:679-683 are not 19. McKeever PJ, Allen SK: Dermatitis associated with Cheyletiella infestation paper readily apparent but when the brushings are in cats. J Am Vet Med Assoc 1979; 174:718-720 placed in 80% alcohol, mites will float to the surface and are 20. Hirst S: On the occurrence of a pseudoparasitic mite (Cheyletiella parasiti- visible to the naked eye. 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